'Dear + name' is the standard formula for beginning letters and emails. 'Name + dear' isn't an accepted written form at all. It's sometimes used as an affectionate term of address in speaking, usually by grandmothers and elderly aunts! If a young person says it, it's often used as a joke. Of course, between friends, in informal situations, you can address people in any way you want. But please be aware that 'Name + dear' is not a standard way of beginning a correspondence.

I would go so far as to say that 'Dear' is no longer 'comfortable' for the majority of people outside of personal correspondence with friends, or coming from someone over the age of 75. Personally, it makes me extremely uncomfortable to be addressed as 'Dear' from someone I don't know, especially a man. I consider it to be inappropriate.

Su Ki is right. Dear Su Ki...... She is also correct that elderly aunts such as myself often reverse things and say, or write, Su Ki dear..... I think elderly aunts such as myself must be very annoying.

In the US, it is only used to start a written letter and would be "Dear Name". It is rarely ever used in conversation.

I think your friend is being polite, cute, or affectionate though as "name + dear" can indicate that too. A similar word for this is "honey". For instance, someone might say "Shawn, honey, you make me laugh so much and bring so much joy to my day."